Bigquery - aggregate while filtering out values - google-bigquery

Question

I'm sure this question has been answered elsewhere but I can't find it.
I have a table of invoices like
id
company
index
date_sent
amount
1
Com1
1
2022-01-01
100
2
Com1
2
2022-02-01
100
3
Com1
3
2022-03-01
100
4
Com1
4
2022-04-01
100
5
Com2
1
2022-02-01
100
6
Com2
2
2022-03-01
100
7
Com2
3
2022-04-01
100
8
Com3
1
2022-01-01
100
9
Com3
2
2022-02-01
100
10
Com4
1
2022-01-01
100
(Index here is added by basically doing RANK() OVER (PARTITION BY co ORDER BY date_sent) as index)
I'd like to return companies who have more than 3 invoices, the aggregate sum of those 3 invoices and the date sent of the 3rd invoice.
For example, for the data above, the returned data should be:
company
date_3rd
amount_sum_3
Com1
2022-03-01
300
Com2
2022-04-01
300
So far I've got:
select company,
(select sum(amount) from grouped_invs.amount_sum_3 amount) as amount_sum_3,
from (
select company,
array_agg(invoices.amount order by invoices.index limit 3) amount_sum_3,
from `data` invoices
group by invoices.company
having count(*) => 3
) grouped_invs
which gives me
company
amount_sum_3
Com1
300
Com2
300
But I can't figure out how to get the 3rd date sent out from there.
Thanks in advance

Answer 1

You might consider below
SELECT (SELECT AS STRUCT
ANY_VALUE(company) AS company,
MAX(date_sent) date_3rd,
SUM(amount) amount_sum_3
FROM grouped_invs.amount_sum_3).*
FROM (
SELECT ARRAY_AGG(invoices ORDER BY index LIMIT 3) amount_sum_3
FROM `data` invoices
GROUP BY invoices.company HAVING COUNT(*) >= 3
) grouped_invs;
Assuming that your data already has an index, below will return same results.
SELECT company, MAX(date_sent) date_3rd, SUM(amount) amount_sum_3
FROM (
SELECT * FROM `data` invoices
WHERE index <= 3
QUALIFY COUNT(*) OVER (PARTITION BY company) >= 3
)
GROUP BY 1;
Query results